I. Field
The following description relates generally to wireless communications, and more particularly to schemes for providing assignments of resources.
II. Background
Wireless communication systems have become a prevalent means by which majority of people worldwide have come to communicate. Wireless communication devices have become smaller and more powerful in order to meet consumer needs, improve portability and convenience. The increase in processing power in mobile devices such as cellular telephones has lead to an increase in demands on wireless network transmission systems.
A typical wireless communication network (e.g., employing frequency, time, and code division techniques) includes one or more base stations that provide a coverage area and one or more mobile (e.g., wireless) terminals that can transmit and receive data within that coverage area. A typical base station can concurrently transmit multiple data streams for broadcast, multicast, and/or unicast services, wherein a data stream is a stream of data that can be of independent reception interest to a mobile terminal. A mobile terminal within the coverage area of that base station can be interested in receiving one, more than one or all the data streams carried by the composite stream. Likewise, a mobile terminal can transmit data to the base station or another mobile terminal.
Most modern data communication systems often employ Automatic Repeat Request (ARQ) mechanism(s) to improve packet transmission reliability. A packet transmission acknowledgement is signaled from the receiver to the transmitter using a low-rate feedback channel. A positive acknowledgement (ACK) indicates to the transmitter that the previous transmission is received correctly and that the receiver is ready for a new packet transmission. A negative acknowledgement (NAK), on the other hand, suggests that an error is detected in the previously transmitted packet and that a retransmission is required.
Generally, there are two categories of packet combining techniques: code combing and diversity combining. In code combining systems, sub-packets are concatenated to form noise-corrupted codewords from increasingly longer and lower-rate codes. An example of a code combing technique is the Type-II Hybrid ARQ (H-ARQ) protocol, where the transmitter responds to the retransmission requests by sending additional party bits to the receiver. The receiver appends these bits to the received packet, allowing for increased error correction capability. In diversity combining systems, the individual symbols from multiple, identical copies of a packet are combined to create a single packet with more reliable constituent symbols.
There are two primary ways of manner for performing HARQ in communication systems: synchronous and asynchronous. To reduce signaling overhead for assignments of resources, the system may employ “synchronous HARQ” and provide support for “sticky” assignments. With synchronous HARQ, the resources for successive retransmissions are not independently scheduled, but rather are allocated for all retransmissions associated with a packet. For example, an assignment of a set of hop-ports applies to one interlace. Assignments on different interlaces are independent, and an access terminal may be given resources on multiple interlaces. For an asynchronous HARQ, the resources are independently scheduled; generally, a new assignment is sent for each resource. Each technique has certain advantages. Most systems today use either synchronous or asynchronous HARQ for assignment of resources. A need exist for a single communication system that would benefit from being able to choose the type of HARQ on an assignment-by-assignment basis.